Bathroom wall around the tub/shower (for under the tiles)

We bought a 1924 house in San Francisco.

As we are fixing up the bathroom, we put up some regular concrete cement backer board around our tub/shower with a layer of transparent plastic under it. It is 1/4" HardieBacker EZ Grid with Moldblock technology.

We were getting ready to tile it, but it turns out that this material is for counter and that it may not be the correct material for the shower wall.